Influences of the Loading on Working Memory on the Spatial Synchronization of Prestimulus Cortical Electrical Activity during Recognition of an Emotional Facial Expression

Abstract

Experiments using a set to an emotionally negative facial expression were performed in healthy adult subjects (n = 35, 16 males, 19 females) to study the effects of increased loading on working memory (addition of an additional cognitive task to the experimental context) on the spatial synchronization of cortical electrical activity. The EEG theta (4–7 Hz) and alpha (8–13 Hz) frequency ranges were studied, along with the alpha1 (8–10 Hz) and alpha2 (11–13 Hz) ranges. Analysis of coherence functions of cortical potentials was compared with data obtained in experiments without loading. Additional loading on working memory led to increases in the inertia of the set to the facial expression and significantly altered the maps of the spatial synchronization of cortical potentials in the theta and alpha ranges: there were increases in the coherence of theta potentials both between individual frontal areas of the left and right hemispheres and between the frontal and temporal areas. It is hypothesized that the inertia of the set to an emotionally negative facial expression is associated with increased activity in the corticohippocampal system, as indicated by the significant increase in coherence relationships between theta potentials in cortical areas which have key roles in organizing cognitive sets. The increase in the loading on working memory significantly weakened the spatial synchronization of the low-frequency alpha rhythm, evidently reflecting decreases in the role of the frontothalamic selective attention system in the recognition process due to redistribution of attention resources resulting from the additional cognitive task in the context of the subject’s ongoing activity.